A Novel Receptor-like Kinase (PnRLK-1) from the Antarctic Moss Pohlia nutans Enhances Salt and Oxidative Stress Tolerance

Plant receptor-like kinases (RLKs) are a group of conserved signaling components that regulate developmental programs and responses to biotic and abiotic stresses. However, only limited information is available on the functions of RLKs in bryophytes. Here, we described the isolation and functional characterization of a RLK gene (PnRLK-1) from the Antarctic moss Pohlia nutans. Sequence alignment and phylogenetic analysis showed that PnRLK-1 was homologous to the cytoplasmic-type RLKs. In addition, subcellular localization analysis in which the transient expression of PnRLK-1-green fluorescent protein was observed in Arabidopsis thaliana mesophyll protoplasts revealed that PnRLK-1 was localized mainly in cytoplasm and a little on plasma membrane. Real-time PCR analysis showed that PnRLK-1 transcriptions were upregulated by mock cold, drought, high salinity, and exogenously supplied abscisic acid (ABA) or methyl jasmonate (MeJA). Overexpression of PnRLK-1 in transgenic Arabidopsis resulted in enhanced plant tolerance to high salinity and H2O2 stresses, and increased plant sensitivity to ABA. Furthermore, the expression levels of stress-responsive genes in transgenic Arabidopsis were also upregulated, including the genes of ABA-dependent signaling pathway (AtABI4, AtABI5, and AtMYB2) and reactive oxygen species (ROS)-scavenging enzymes (AtAPX1, AtZAT10, and AtCAT1). Therefore, we proposed that PnRLK-1 was a novel RLK involving in the adaptation of the Antarctic moss to the polar environment, increasing the salt and oxidative tolerance as well as the ABA sensitivity.